package com.company;

public class MyLinkedList implements IList  {

    static class ListNode{//内部类
        public ListNode prev;//结点的前驱
        public ListNode next;//结点的后继
        public int val;

        public ListNode(int val){
            this.val = val;
        }
    }
    //类成员
        public ListNode head;//头结点
        public ListNode last;//尾结点

    //头插法
    @Override
    public void addFirst(int data) {
        ListNode node = new ListNode(data);
        if(head == null){
            head = last = node;
        }else{
            node.next = head;
            head.prev = node;
            head = node;
        }
    }

    //尾插法
    @Override
    public void addLast(int data) {
        ListNode node = new ListNode(data);
        if(head == null){
            head = last = node;
        }else{
            last.next = node;
            node.prev = last;
            last = node;
        }
    }

    //寻找下标为 index 的结点
    private ListNode findIndex(int index){
        ListNode cur = head;
        while (index != 0) {
            cur = cur.next;
            index--;
        }
        return cur;
    }

    //任意位置插入结点
    @Override
    public void addIndex(int index, int data) {
        int len = size();
        if(index<0||index>size()){
            return;
        }
        if(index == 0){
            addFirst(data);
            return;
        }
        if(index == len){
            addLast(data);
            return;
        }
        ListNode node = new ListNode(data);
        ListNode cur = findIndex(index);
        cur.prev.next = node;
        node.next = cur;
        node.prev = cur.prev;
        cur.prev = node;
    }

    //查找是否包含 key 在链表中
    @Override
    public boolean contains(int key) {
        ListNode cur = head;
        while (cur!=null){
            if(cur.val == key){
                return true;
            }
            cur = cur.next;
        }
        return false;
    }


    @Override
    public void remove(int key) {
        ListNode cur = head;
        while(cur!=null){
            if(cur.val == key){
                //删除
                if(cur == head){
                    head = head.next;
                    if(head != null) {
                        head.prev = null;
                    }
                }else {
                    cur.prev.next = cur.next;
                    if (cur.next == null) {
                        last = last.prev;
                    } else {
                        cur.next.prev = cur.prev;
                    }
                }
                return;
            }
                cur = cur.next;
        }
    }

    @Override
    public void removeAllKey(int key) {
        ListNode cur = head;
        while(cur!=null){
            if(cur.val == key){
                //删除
                if(cur == head){
                    head = head.next;
                    if(head != null) {
                        head.prev = null;
                    }
                }else {
                    cur.prev.next = cur.next;
                    if (cur.next == null) {
                        last = last.prev;
                    } else {
                        cur.next.prev = cur.prev;
                    }
                }

            }
            cur = cur.next;
        }
    }

    //求链表的长度
    @Override
    public int size() {
        if(head == null){
            return 0;
        }
        ListNode cur = head;
        int count = 0;
        while (cur!=null){
            count++;
            cur = cur.next;
        }
        return count;
    }

    //清空链表
    @Override
    public void clear() {
        ListNode cur = head;
        while (cur!=null){
            ListNode curN = cur.next;
            cur.prev = null;
            cur.next = null;
            cur = curN;
        }
    }

    //打印链表
    @Override
    public void display() {
        ListNode cur = head;
        while (cur!=null){
            System.out.print(cur.val+" ");
            cur = cur.next;
        }
        System.out.println();
    }
}
